Bogs at full throttle

[74bigblock]

O.K. I've got the new tank, sending unit etc.. in my garage awaiting it's final resting place.... in the car!!!

One thing I noticed is that the sending unit is not quite the same... the one I pulled out has a 90 degree bend in it, and this one is a bit more... I'd say 120. Will this be a problem?

 

[vettepilot]

If I remember correctly (I don't have a service manual or illustration available) the swing arm was about a 120 degree angle. Quite possible the original sending unit was already damaged before it got to you.
I may be wrong so lets see if somebody with the proper reference can answer.

vettepilot

 

[Roy]

Flat Spot

Fatten the fuel-air mixture by increasing the size of your main jets. You can also fatten the fuel/air mixture by raising the float level.

The problem is not the vacuum hose to the tranny as if there was a leak in vacuum, it would occur at all times while the engine is running. By the way, this little hose does deteriorate and leak. It is easy and cheap (25 cents) to replace.

K&N, besides being a terrible filter, allows much more air (and dirt) than normal through the carb.

 

[74bigblock]

74 454 ... original intake, Edelbrock Performer 750 carb. She runs great at 50% throt., but any more than this, she starts to choke out. I'm thinking it might be the fuel pump, but would appreciate any other things to check. I have already re adjusted the mixture screws with no improvement.

First of all... lets refresh here for a sec... no quadrajet, no rochester. Edelbrock. I have an Edelbrock Performer 750. This means... I have no jets, I have metering rods. It also means I cannot adjust the floats per se, I would need to change the rods. After seeing the amount of rust in the tank, lines, and filter... I am 99.9% positive that this is the bog issue. It would explain the car running fine at moderate throtle, but not being able to get enough fuel for the jump to light speed, causing the car to bog/choke/stall/fart, whatever. It also would explain that the car did run great when I first picked it up... as it sat for quite a while... thus the rust settled in the tank. Once I started driving her a lot, the rust was stirred up, and entered the fuel system, clogging the sending unit, lines, pump, filter, and hopefully not the carb. Second... Lets take one thing at a time, and see what happens. I will install the tank tomorrow (Saturday 11/1) and let you all know if it makes a difference. Third, I ordered the Hooker side mount chrome headers and side pipes , so say goodbye to my exhaust leak also (should be delivered sometime next week).

 

[74bigblock]

OK... so we went to change the fuel pump, and it came off just fine. Now we can't get it back on. WTF???? We tried both the new pump, and the old pump, both now seem to fit funny. Is there some sort of ajustment we need to make before just bolting this think back on? Cause it doesn't want to fit on there.

AKKKK! ad

 

[Roy]

Are you pushing the rod up inside the engine when you attempt to mount the fuel pump? If it drops down it will block the pump from mounting.

 

[76L82]

74Big block - You would think that the "lever" arm on that mechanical fuel pump would compress in your hand..but it doesn't. Therefore, when you slide the lever inside the mounting plate of the block..the fuel pump push rod needs to be seated inside the block and not allowed to slide out. What is probably happening is that when you go to push the lever in..the push rod has already slid down a little lower than where your lever needs to be...of course you can't see this happening because the only view you'll be getting is straight on at the outside of the fuel pump. As a single person operation this can really take some time...as the push rod slides back out at will. A lot of texts say to apply a heavy grease to it so that it will seat in the block for the few seconds that you need to start bolting the pump to the block. It takes a few times..but you'll feel it almost immediately if the push rod stays seated...your bolts will grab and the lever will start to compress inside the mounting plate just enough to get the pump on.

On your first problem about bogging make sure that your vacuum modulator is creating enough vacuum so that your kickdown cable on your transmission is working. I find that on my 70 Cam SS with a 600 Edelbork Performer that if my kickdown cable is not adjusted perfect...and I mean perfect...I'll be thinking my transmission is kicking down a gear (TH350) but it isn't...for that time while I am trying to be WOT...she bogs down. I let off the gas for a second and then do it again..and I convince myself it downshifted but nothing really happened but more bogging.

Got the adjustment on my kickdown cable perfect, rechecked my timing and it has become a different car. A lot of guys do different things, but I get my best vacuum for the modulator hooked up to the back of my intake manifold. Good luck!

 

[74bigblock]

OK yeah the rod did drop down, Realized this after I posted.... When we went back down and played with it.. we could not get the rod to budge even a 1/4 inch. How the hell do you get it back up into the block??? There is a square bolt directly underneath it.. does this have anything to do with it? We are totally frustrated at this point.. not to mention drunk!

 

[vettepilot]

There should be a hex head bolt on the front of the block adjacent the pump cavity. Remove that bolt, push the pump rod all the way up in it's bore, then install a longer bolt and finger tighten the bolt against the pump rod. this will hold it in place until the pump is installed. To make it easier, hand turn the engine until the pump cam lobe is positioned so that the pump rod is as far up as it will go. If you do all this, the pump should slip in with little effort.

******REMEMBER******
remove the long bolt, and replace the short one removed in the first step, or the pump will not work.

vettepilot

 

[74bigblock]

Vettepilot,

There is no hex bolt om the front of the block... there are no bolts period in that area. we tried to hand turn the engine, but could not overcome the compression. The pump rod is totally jammed in there.

 

[vettepilot]

uh oh,
I'll think on this, trying to remember and visualize the big block engine. Hopefully somebody else can lend some thought.

vettepilot

 

[74bigblock]

So we got everything hooked up, got the rod pushed up into the block.... and it seems that the new pump is non fucntional. Gas would not come up the lines, and we turned her over quite a bit. I even gave the lines a proverbial BJ and got the gas up, but it would pump gas to the carb. So... we are considering buying a nother new pump, reusing the old one, or just saying F&*$ it, and doing an electric pump system and blocking off the manual with a plate. What do you all think?

 

[silver 80]

Are you sure it's the right pump for that engine?
I was helping a friend do the same thing, the parts person gave him the wrong pump looked the same but the throw was different and kept breaking the pump.

 

[vettepilot]

Agree with the above, also a few things to check:

1. Make sure that the rod is actually hitting the fuel pump arm. With all the installation problems you already had it could be off to one side, I would double check the fuel pump arm to make certain it is centered. Rare, but this has been known to happen.

2. Did you check to make sure the cam doesn't have a worn fuel pump lobe?

3. Does the pump "draw" (build suction) on the intake side port when you actuate it by hand out of the engine?

vettepilot

 

[74bigblock]

Yeah, I double checked with Mid America, It is the correct for the 74 454, and they are replacing for me.

 

[74bigblock]

We know that it the cam was working properly before we started the project... it's also a new cam... so I t could not be worn.. has about 500 miles on it. The tolerance is so tight in the port for this pump there is no way it could be off center... the only thing I can think of is that the unit is bad, or the rod is somehow stuck in the up position... but it was pretty tight when we installed... so I am really thinking it's a fluke bad unit. Total pain though... it is in the most awkward spot I could think of to put a pump.

 

[74bigblock]

Success!!!

OK so after all this work, we have found the causes of the bog.

1) Fuel line went from 3/8 up to firewall, then down to 5/16. We yanked out the 5/16 and replaced with 3/8 all the way up.

2) Abrasions on fuel pump push rod caused it to hang up on the wall of the block.... so bad that we could not get the rod out (normally it's a PITA to get the thing to stay in, we thought this was ironic).

3) Rust in the tank caused a partial block in the fuel lines where it switched from 3/8 to 5/16. We replaced the tank, and sending unit in addition to step 1.

4) For sh*ts and giggles I ordered Hooker chrome headers and sidepipes to give me a little bit more smile.

5)Dyno Tunning is taking place this week, and once we have a final number, I'll post the results and pictures for you all.

At this time I'd like to thank all of you who replied! It's great that a forum like this exists.

Thanks again!
Dave